1. Technical Field
The disclosure generally relates to coding circuits, and particularly, to a key coding circuit used in electronic devices.
2. Description of the Related Art
Various matrix scanning circuits are widely used in different electronic devices with keypad input, such as mobile phones and notebook computers, whereby the keys are scanned to confirm activation thereof. FIG. 3 shows an existing matrix key circuit including keys S0˜S15 and a key coding circuit 10.
The key coding circuit 10 includes line output ports PA0˜PA3 and column output ports PA4˜PA7. Both ends of each key are respectively connected to a line output port and a column output port. In use, the key coding circuit 10 provides high levels sequentially to the output ports PA0˜PA3 and provides low levels to the output ports PA4˜PA7. When any key is used, the high level of the line output port is converted to low level; the key coding circuit 10 detects the level changes to read corresponding procedures, resulting in scanning matrix keys line by line to indentify the specific location of the used key, which increases the scan time.
Therefore, there is room for improvement within the art.